1. Field of the Invention
The present invention is directed to a method for producing a p-doped semiconductor region in an n-conductive semiconductor body through joint diffusion of aluminum and boron under controlled conditions.
2. Description for the Prior Art
A method of the type herein described is known from J. Electrochem. Soc. Volume 125, No. 6, June 1978, pages 957-962. In the method described in that article, a plurality of wafer shaped semiconductor bodies is introduced into a quartz tube together with a plurality of dopant sources composed of aluminum blocks. The quartz tube is connected to a vacuum pump which evacuates it down to at least 10.sup.-6 Torr. Subsequently, a diffusion furnace is mounted over the evacuated quartz tube and the latter is exposed to a diffusion temperature of, for example, 1150.degree. C. over a predetermined time interval. The disadvantage of this procedure is that the inside wall of the quartz tube must first be passivated in order to prevent a lowering of the partial aluminum pressure during the diffusion as a result of the influences of the quartz tube on the liberated aluminum vapor. A separate method step is required wherein a plurality of dopant sources are introduced into the quartz tube and, following a prior evacuation, the tube is exposed to a temperature of 1100.degree. C. over a time interval of about 120 minutes. The aluminum molecules emerging from the dopant sources permit a passivation layer to form at the inside wall of the quartz tube.